Double negation operator

-- Value -- Value

Value

The value to convert.

Returns

Number Number

0 If the given operand is FALSE, 1 if it is TRUE and the unchanged operand if it is a number.

Returns 0 if the given operand is FALSE, 1 if it is TRUE and the operand unchanged if is a number. -- FALSE -- FALSE returns 0 and -- TRUE -- TRUE returns 1.

This operator is typically used to convert an array of logical values to an array of numbers. This formula returns the array { 1, 0, 0 }{ 1; 0; 0 }:

-- { TRUE, FALSE, FALSE }

-- { TRUE; FALSE; FALSE }

This is useful in a variety of situations — refer to the examples below.

The TONUMBER function is similar, but can also convert text strings.

Examples

-- FALSE

Returns 0.

-- { FALSE, TRUE }

-- { FALSE; TRUE }

Returns the array { 0, 1 }{ 0; 1 }.

SUM ( -- ({ 1, 2, 3, 4, 5 } > 3))

SUM ( -- ({ 1; 2; 3; 4; 5 } > 3))

Returns the number of array members which are greater than 3. (In this case, only 4 and 5 are greater than 3, meaning that 2 is returned.) When applied to { 1, 2, 3, 4, 5 }{ 1; 2; 3; 4; 5 } and 33, > returns a logical array with the same number of elements as the { 1, 2, 3, 4, 5 }{ 1; 2; 3; 4; 5 } number array, where individual logical values indicate if the corresponding number in the number array is greater than 3. In other words, { 1, 2, 3, 4, 5 } > 3{ 1; 2; 3; 4; 5 } > 3 returns { FALSE, FALSE, FALSE, TRUE, TRUE }{ FALSE; FALSE; FALSE; TRUE; TRUE }, which the -- operator turns into { 0, 0, 0, 1, 1 }{ 0; 0; 0; 1; 1 }. Finally, the SUM functions adds together all elements, yielding 2.

SUM ( -- ( ISODD ({ 1, 2, 3, 4, 5 })))

SUM ( -- ( ISODD ({ 1; 2; 3; 4; 5 })))

Returns the number of array elements which are odd. The ISODD function returns the logical array { TRUE, FALSE, TRUE, FALSE, TRUE }{ TRUE; FALSE; TRUE; FALSE; TRUE }, indicating that 11, 33 and 55 are odd, whereas 22 and 44 are even. The -- operator then turns that logical array into the number array { 1, 0, 1, 0, 1 }{ 1; 0; 1; 0; 1 }. When given that array, the SUM function returns 3, indicating that three of the array elements are odd.

SUM ( -- ( ISODD ({ 1, 2, 3 }) || ({ 1, 2, 3 } > 1)))

SUM ( -- ( ISODD ({ 1; 2; 3 }) || ({ 1; 2; 3 } > 1)))

Returns the number of array elements which are odd or are greater than 1. All array elements qualify, meaning that 3 is returned. ISODD ({ 1, 2, 3 }) ISODD ({ 1; 2; 3 }) returns the logical array { TRUE, FALSE, TRUE }{ TRUE; FALSE; TRUE }, because only 1 and 3 are odd numbers. { 1, 2, 3 } > 1{ 1; 2; 3 } > 1 returns the logical array { FALSE, TRUE, TRUE }{ FALSE; TRUE; TRUE }, as the array elements 2 and 3 are greater than 1. The || operator ("logical or") returns the logical array { TRUE, TRUE, TRUE }{ TRUE; TRUE; TRUE }, because every element of the array { 1, 2, 3 }{ 1; 2; 3 } is either odd, or is greater than 1. When given that array, after the -- operator has turned it into a number array, the SUM function returns 3, indicating that three of the array elements are either odd or are greater than 1.

SUM ( -- ( ISODD ({ 1, 2, 3 }) && ({ 1, 2, 3 } > 1)))

SUM ( -- ( ISODD ({ 1; 2; 3 }) && ({ 1; 2; 3 } > 1)))

Returns the number of array elements which are both odd and are greater than 1. Only the array element 3 qualifies, meaning that 1 is returned. ISODD ({ 1, 2, 3 }) ISODD ({ 1; 2; 3 }) returns the logical array { TRUE, FALSE, TRUE }{ TRUE; FALSE; TRUE }, because only 1 and 3 are odd numbers. { 1, 2, 3 } > 1{ 1; 2; 3 } > 1 returns the logical array { FALSE, TRUE, TRUE }{ FALSE; TRUE; TRUE }, as the array elements 2 and 3 are greater than 1. The && operator ("logical and") returns the logical array { FALSE, FALSE, TRUE }{ FALSE; FALSE; TRUE }, which is FALSE for the first element 1 (as it isn't greater than 1), is FALSE for the second element 2 (as it isn't odd) and is TRUE for the third element 3 (as it is both greater than 1 and is odd). When given that array, after the -- operator has turned it into a number array, the SUM function returns 1, indicating that one element of the original array is both odd and is greater than 1.